Contemporary cellular radio systems, or mobile telecommunication systems, provide an over-the-air interface to wireless mobile stations (MSs), also referred to as user equipments (UEs), via a radio access network (RAN) that interfaces with at least one core network. The RAN may be implemented as, for example, a CDMA2000 RAN, a Universal Mobile Telecommunications System (UMTS) RAN, a Global System for Mobile communications (GSM) RAN, or another suitable radio access network implementation. The MSs may comprise, for example, a mobile terminal such as a mobile telephone, a laptop computer featuring mobile telephony software and hardware, a personal digital assistant (PDA), or other suitable equipment adapted to transfer and receive voice or data communications with the radio access network.
A RAN covers a geographical area comprised of any number of cells each comprising a relatively small geographic area of radio coverage. Each cell is provisioned by a cell site that includes a radio tower, e.g., a base transceiver station (BTS), and associated equipment. BTSs communicate with MSs over an air interface within radio range of the BTSs.
Numerous BTSs in the RAN may be communicatively coupled to a base station controller (BSC), also commonly referred to as a radio network controller (RNC). The BSC manages and monitors various system activities of the BTSs serviced thereby. BSCs are typically coupled with at least one core network.
BTSs are typically deployed by a carrier network in areas having a high population density. The traffic capacity of a cell site is limited by the site's capacity and affects the spacing of cell sites. In suburban areas, sites are often up to two miles apart, while cell sites deployed in dense urban areas may be as close as one-quarter of a mile apart. Because the traffic capacity of a cell site is finitely limited, as is the available frequency spectrum, mobile operators have a vested interest in technologies that allow for increased subscriber capacity.
A microcell site comprises a cell in a mobile phone network that covers a limited geographic area, such as a shopping center, hotel, airport, or other infrastructure that may have a high density mobile phone usage. A microcell typically uses power control to limit the radius of the microcell coverage. Typically a microcell is less than a mile wide.
Although microcells are effective for adding network capacity in areas with high mobile telephone usage, microcells extensively rely on the RAN, e.g., a controlling BSC and other carrier functions. Because contemporary BSCs have limited processing and interface capacity, the number of BTSs—whether microcell BTSs or typical carrier BTSs—able to be supported by the BSC or other RAN functions is disadvantageously limited.
Contemporary interest exists in providing enterprise and office access, including small office/home office (SOHO) radio access, by an even smaller scale BTS. The radio coverage area of such a system is typically referred to as a femtocell. A femtocell typically provides radio network access on an over-the-air interface to mobile stations within its coverage area and connects to the service provider's network via broadband (such as DSL or cable). A femtocell thus allows service providers to extend service coverage indoors, especially where access would otherwise be limited or unavailable. Current designs typically support 2 to 4 active mobile phones in a residential setting, and 8 to 16 active mobile phones in enterprise settings.
In a system featuring a femtocell, an MS may be authorized to operate in the femtocell when proximate the femtocell system, e.g., while the MS is located in the SOHO. When the MS moves beyond the coverage area of the femtocell, the MS may then be serviced by the carrier network. The advantages of deployment of femtocells are numerous. For instance, mobile users frequently spend large amounts of time located at, for example, home, and many such users rely extensively on cellular network service for telecommunication services during these times. For example, a recent survey indicated that nearly thirteen percent of U.S. cell phone customers do not have a landline telephone and rely solely on cell phones for receiving telephone service. From a carrier perspective, it would be advantageous to have telephone services provisioned over a femtocell system in which the main communication bandwidth is performed over the IP network, e.g., deployed in the user's home, to thereby reduce the load and effectively increase the capacity on the carrier RAN infrastructure.
One disadvantage of existing femtocell systems is that each femtocell is limited to a very limited geographic area, making the femtocell system inconvenient for deployment in larger enterprises. What is required is a system and method for providing expanded coverage using the femtocell concepts.